This application is the National phase under 35. U.S.C. xc2xa7 371 of PCT International Application No. PCT/EP99/07843, which has an International filing date of Oct. 15, 1999, which designated the United States of America.
The invention relates to a multipole plug-and-socket connection according to the preamble of the main claim.
Plug-and-socket connections of this kind are known. (Main catalogue of the firm W. W. Fischer SA, Switzerland, 1997 edition). For easy position location when assembling the plug and socket or coupling, either metal semicylindrical shells are to be provided both at the plug and at the socket/coupling, these complementing one another when correctly assembled to form a complete cylinder surrounding the plug-and-socket connection, or, if the intention is to prevent structurally similar plug-and-socket connections from being confused, a plurality of part-cylindrical shells distributed over the circumference are to be provided, for example two quarter-cylindrical shells at the plug and two quarter-cylindrical shells at the socket/coupling (Fischer Catalogue, Section L, page 4: Codings for position location when plugging in).
In order to make plug-and-socket connections of this kind EMC-tight, a metal plug housing is used which on the one hand is electrically connected to the cable screening and which establishes electrical contact with the housing, also consisting of metal, of the socket or coupling when assembled. This earth contact, previously only possible via the plug housing, for the cable screening is complex and not optimum in electrical terms.
The object of the invention is therefore to develop and improve a multipole plug-and-socket connection of the indicated type so as to achieve optimum earth contact between the plug and the socket or coupling both in electrical and mechanical terms.
Taking a multipole plug-and-socket connection according to the preamble of the main claim as a starting point, this object is solved by the characterising features of this claim. The subclaims comprise advantageous developments.
According to the invention, the metal part-cylindrical shells, which are in any case provided in plug-and-socket connections of this kind for mechanical position location, are modified in a simple and inexpensive manner so as to be simultaneously used to establish electrical earth contact. At least one additional contact spring element is formed for this purpose at least at one of the longitudinal edges of at least one of the part-cylindrical shells, this element establishing electrical cross-contact between the longitudinal edges of the part-cylindrical shells in the assembled state. Therefore all that is required to establish earth contact in the plug-and-socket connection is to establish a metallic connection in the plug between the cable screening and the part-cylindrical shell and to metallically connect, in the associated socket or coupling, the part-cylindrical shell located here to the earth of the device accommodating the socket or to the cable screening adjoining the coupling, as has been standard practice until now where such plugs and sockets or couplings are concerned.
When using the invention in plugs with a metal plug housing which encloses the part-cylindrical shells and is only separated from these by a narrow gap, a slight expansion of the part-cylindrical shells complementing one another to form a complete cylinder is achieved in the assembled state via the contact spring element. The individual part-cylindrical shells are thereby pushed outwards slightly, so that they establish electrical contact with the cylindrical inner surface of the metal plug housing by way of their outer surface. The earth connection between the plug and socket or coupling is improved further as a result.
As the plug housing is no longer needed for earth contact in the plug-and-socket connection according to the invention, it may consist completely of non-conducting plastics material. A plug-and-socket connection according to the invention can be assembled at a very low cost from a few individual parts while still guaranteeing effective and reliable earth contact connection in the assembled state. The contact spring elements establishing the cross-contact between the part-cylindrical shells may be produced in different ways at the longitudinal edge. In the case of small to medium-sized plugs whose part-cylindrical shells consist of thin spring plate, the contact spring element may be produced by a single longitudinal slot extending parallel to the longitudinal edge or by a plurality of short longitudinal slots formed one behind the other in the spring plate shell, with the narrow spring plate web or spring plate webs thereby formed and connected to the shell on one or both sides being bent outwards slightly. In the case of larger plugs whose part-cylindrical shells have thicker walls, the contact spring elements may consist of repeatedly folded plate webs which are worked out of the part-cylindrical shells via slots, or contact spring parts, which are optionally separate, may be inserted in corresponding edge recesses in the part-cylindrical shells.
The contact springs are distributed over the part-cylindrical shells such that no torsional forces are exerted on the part-cylindrical shells used for position location when assembly takes place. With regard to a multipole plug-and-socket connection with semicylindrical shells provided at the plug or socket/coupling, as are most common in practice, contact spring elements are only provided at one of the semicylindrical shells, preferably at that of the plug, this being at both longitudinal edges. This prevents the semicylindrical shells, which complement one another to form a complete cylinder, from turning in one direction upon assembly and then losing the predetermined orientation between the plug pins and the female contacts and therefore no longer guaranteeing the object of exact position location during assembly.
As the mechanical construction provided for position location is maintained in the invention, a plug additionally equipped according to the invention with contact springs is entirely compatible with sockets or plug couplings commonly used until now.